Technical Field
The present invention relates to a sample dispenser for an analysis device for analyzing a liquid or gaseous sample, in particular to an analysis device operating according to the principle of chromatography.
Description of the Related Art
The invention is in particular applicable in the field of liquid chromatography (LC), high performance liquid chromatography (HPLC) or gas chromatography (GC).
Nowadays, liquid chromatography, high performance liquid chromatography (HPLC) or gas chromatography use a fixed high-pressure injection valve for sample injection. The high-pressure injection valve is typically a rather complex component, which comprises several ports and can be switched between an intake position and an injection position. To render the analyses as accurate as possible, it is necessary to evenly apply a mobile phase to the respectively utilized separating columns. It is therefore important that the switching of the injection valve affects the flow of the mobile phase over the separating column as minimally as possible. Furthermore, possible contamination sources must of course be eliminated to the greatest extent possible. This is especially problematic when many samples are to be analyzed successively.
U.S. Pat. No. 3,918,913 shows an example of a common sample dispenser system used in liquid chromatography, in which a so-called 6-port valve is used for sample injection. The 6-port valve has a substantially rotational-symmetric configuration with a valve body and an actuator that is rotatable about a valve axis. The valve body is provided with 6 ports, wherein two selected adjacent ports can be connected with each other by rotating the actuator. A first port of the valve body constitutes an eluent inlet, i.e., via this port, eluent, which constitutes the mobile phase flowing over the separating column—if applicable, having a substance to be analyzed added thereto—is supplied. Another port of the valve body is associated with the separating column, i.e., constitutes a column outlet for supplying an eluent, or an eluent having a substance to be analyzed added thereto, to the separating column. The other four ports of the valve body are associated with a sample dispenser system. Two of these four ports of the sample dispenser system are in permanent fluid connection via an external sample loop. One port of the sample dispenser system serves as a sample intake for supplying the sample to be analyzed. Another port is typically connected to a metering pump or the like in order to receive the sample to be analyzed in the sample loop and discharge it again, if applicable.
In an intake position of the injection valve, the eluent inlet is connected with the column outlet and the four ports of the sample dispenser system are interconnected such that a substance to be analyzed (hereinafter also briefly referred to as sample) can be received in the sample loop through the sample inlet. By rotating the injection valve into an injection position, the sample loop can then be switched into fluid connection with the eluent inlet and the column outlet such that the sample is mixed with eluent and reaches the separating column.
In the injection position of the injection valve, surplus sample volume can be removed via the remaining two ports of the sample dispenser system. Before analyzing another sample, the complete sample dispenser system needs to undergo a complex washing procedure to avoid contamination. This is in particular problematic in the region of the sample loop, as impurities remaining in this region directly reach the separating column, while this region can however only be washed by means of the eluent stream, i.e., after injecting the sample and switching the injection valve back to the intake position. In particular in HPLC applications, the contamination of the sample loop is a problem that is difficult to manage, as the sample loop is, in the intake position of the injection valve, filled and washed at relatively low pressures, while in the injection position, it is, however, subject to the high pressure with which the eluent/sample stream is pressed onto the separating column.
A disposable sample intake device which can be used in a sample loop of an injection valve for HPLC is known from DE 10 2007 000 622 A1. Said disposable sample intake device consists of a container for receiving a sample volume, which can be coupled to the sample loop by means of a first coupling arranged on an upstream end of the container and a second coupling arranged on a downstream end of the container. The container is, via the first or the second coupling externally filled with sample volume and then placed in the sample loop by means of the first and the second coupling. The eluent stream is then supplied to the sample loop via the 6-port injection valve. After the analysis is completed, the injection valve is switched back to the intake position and the disposable container in the sample loop can be replaced by a new disposable container containing the next sample to be analyzed. A similar sample dispenser system for HPLC applications is known from WO 2010/084180, in which the pipette tips are adapted to be placed in the sample loop as disposable containers.